Process and device for monitoring a patient during anesthesia and for determining the combined effect of a plurality of anesthetics

ABSTRACT

A process is provided for monitoring a patient being anesthetized, as well as a process for determining a combined effect of different anesthetics used. Devices for carrying out the processes are also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. §119 ofGerman Patent Application DE 10 2007 030 505.4 filed Jun. 30, 2007, andDE 10 2007 038 975.4 filed Aug. 17, 2007 the entire contents of each ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention pertains to a process for monitoring a patientbeing anesthetized by means of at least one anesthetic with the use of amonitoring device, which has a display means for displaying informationconcerning the anesthetic. The present invention pertains furthermore,to a device for monitoring a patient being anesthetized by means of atleast one anesthetic with a display means for displaying informationconcerning the anesthetic.

The present invention pertains, furthermore, to a process fordetermining a combined anesthetic effect for a patient beinganesthetized by means of a combination of active ingredients and adevice for determining a combined anesthetic effect for a patient beinganesthetized by means of a combination of active ingredients.

BACKGROUND OF THE INVENTION

It shall be ensured for adequate anesthesia that the patient will notremember the procedure, the responses to painful stimuli are suppressedand circulation and respiration are maintained despite the highly potentdrugs necessary for this, and the oxygen supply of the brain and otherorgans is thus guaranteed at any time. It shall be ensured for this thatthe drugs used for the anesthesia are present at a reasonableconcentration at their sites of action, e.g., in the brain in the caseof centrally acting anesthetics, such as sedatives or centrally actinganalgesics, such as opiates, or at the motor end plates between motornerves and skeletal muscles in the case of paralyzing drugs, e.g.,muscle relaxants. The necessary concentration may differ depending onthe situation, e.g., due to the surgical procedures being performed. Forexample, the pain stimulus elicited by a skin incision in the upperabdominal region may be markedly weaker than the pain stimulus caused byincisions for resecting a kidney.

If the need for anesthetic action changes in the course of, e.g., asurgery, an adequate anesthesia shall ensure that this need is met asquickly as possible.

However, adequate anesthesia is characterized at the same time by theanesthetic drugs not being dispensed at excessively high doses, in orderto, among other things:

-   -   minimize adverse side effects of the drugs used for the        anesthesia, such as a secondary weakening of the intensity of        contraction of the heart muscle or respiratory depression; and    -   prevent avoidably high concentrations of anesthetic active        ingredients from accumulating in endogenous storage sites or        compartments such as fatty tissue, which excessively delay the        desired end of an anesthesia due to reflooding.

Achieving adequate anesthesia is especially challenging for ananesthesiologist, among other things, because the concentrations ofanesthetic active ingredients in the blood or at the site of action andthe anesthetic effects resulting therefrom, such as analgesia, sedationand paralysis, are unknown to the anesthesiologist or are known to theanesthesiologist to a greatly limited extent only. This is especiallytrue of drugs that are administered intravenously (i.v.). The situationis further aggravated by the fact that more than one anesthetic drug isoften administered, and that especially the analgesics (e.g., opiates)and sedatives (e.g., propofol) synergistically interact with each other.For example, the degree of increase in the effect of propofol followingan increase in the concentration of propofol at the site of actiondepends on an opiate concentration that is likewise present at the siteof action.

Technical solutions, which can facilitate the control of an adequateanesthesia for the anesthesiologist, are known from the state of theart:

-   -   a. The effect of muscle relaxants can be measured directly, even        though only on selected skeletal muscles, and not always on        skeletal muscles that are relevant for the particular procedure        (e.g., the thumb muscle).    -   b. The concentration of volatile anesthetic drugs can be        measured during expiration in the breathing gas. The        end-expiratory concentration thus measured reflects the        concentration in the lungs. However, it reflects the        concentration in the blood plasma to a limited extent only, and        that in other tissues or at the site of action to an even more        limited extent only.    -   c. The monitoring of electrical voltages between certain sites        on the scalp (EEG) makes it possible to infer the electrical        activity in the brain. Devices are known, by means of which        these voltage signals can be interpreted by means of very        demanding processes of digital signal processing and aggregated        into a standardized value, which is in a—not always        close—relationship with the depth of sedation of the patient.        One example of such a device is the BIS™ monitor from the firm        of Aspect Medical.    -   d. Processes are known by means of which the concentration        curves of anesthetic drugs can be determined and predicted on        the basis of models based on the knowledge of the quantities of        drugs introduced into the patient intravenously or via the        lungs. These models have been determined based on measurements        on a plurality of patients and permit a certain adaptation to        the patients actually involved by stating the age, body weight,        etc., of the patient to be actually treated. These processes        fall in the area of pharmacokinetics.    -   e. Furthermore, processes are known by means of which the        anesthetic effects of the drugs being used can be determined        from the quantities of active ingredient administered. These        effects are frequently represented as a probability that a        patient responds to a given stimulus (e.g., a skin incision or        being spoken to/shaken). These probabilities are based on        statistical models, which have been determined on the basis of        measurements on a plurality of patients. These models can also        describe the mutual interaction of a plurality of anesthetic        drugs. These processes fall in the area of pharmacodynamics.    -   f. Furthermore, processes for the graphic display of        pharmacokinetically and pharmacodynamically determined        concentration and effect curves are known. These include        displays on the time axis (time-based display) as well as        displays of opiate concentrations versus sedative concentrations        (concentration-based display as is described in Patent DE 10        2004 050 717 B3 and corresponding US2006081244—U.S. patent        application Ser. No. 11/250,026 of Oct. 13, 2005, which is        hereby incorporated by reference).

Besides the adequate anesthesia, as it was described above, theanesthesiologist also has the task of monitoring and possibly securingbodily functions, which are limited or threatened based on side effectsof the anesthetic drugs, based on therapeutic or surgical procedures, orbased on a disease of the patient. These bodily functions include, e.g.,the blood pressure, body temperature and respiration.

A number of possibilities of procedures, e.g., hemodynamically activedrugs, volume replacement (e.g., physiological sodium chloridesolution), heating or cooling techniques and respirators, are availableto the anesthesiologist to perform these tasks. To make possible theadequate control of the use of these possibilities of procedure, variousmeasurement methods, by means of which relevant physiological variablesor surrogates thereof can be measured, are available to theanesthesiologist. These include, e.g., the end-expiratory CO₂concentration measurement, invasive or non-invasive blood pressuremeasurement, heart rate measurement, etc.

SUMMARY OF THE INVENTION

Against this background, the basic object of the present invention is toprovide a process for monitoring a patient being anesthetized, whichenables the anesthesiologist to better care for a patient beinganesthetized during an adequate anesthesia as discussed above andespecially to dispense the anesthetics more adequately. In addition, asuitable device and an anesthesia device are to be provided.

According to one aspect of the invention, a process is provided formonitoring a patient being anesthetized by means of one or moreanesthetic. The process comprises the step of providing a monitoringdevice having a display means for displaying information concerning theone or more anesthetic and displaying physiological states (heart rate,MAP, et CO₂) of the patient, which are variable during the anesthesia,by means of the display means.

Thus, the present invention provides a process for monitoring a patientbeing anesthetized with at least one anesthetic with the use of amonitoring device, which has a display means for displaying current orrelevant information concerning the anesthetic. In addition,physiological states of the patient, which change in the course of theanesthesia, are displayed by means of the display means.

An anesthetic is defined within the framework of the present inventionas any drug known as an anesthetic or an active ingredient on which itis based and also combinations thereof, regardless of whether it is avolatile drug or a drug administered intravenously (by an i.v.). Thedefinition of an anesthetic in the sense of the present invention alsoincludes any drug that does not fall within the class of the typicalanesthetics but which is likewise to be taken into account in connectionwith the anesthesia by the anesthesiologist when carrying out thepresent invention. The latter drugs and/or active ingredients includeespecially sedatives. In particular, drugs that have relevantinteractions with the anesthetics being used, which are popularly calledas such, are also included among the anesthetics here.

The “patient” of the present invention may be a human being, but thepresent invention may also be used in animals being anesthetized.

The physiological states of the patient, which are likewise displayed onthe display means, can be indicated by measured values of hemodynamic,respiratory or other parameters or surrogates thereof, which aresuitable for estimating the patient's status and are relevant for theanesthesiologist. Depending on the type of the therapeutic or surgicalprocedure, different physiological states can be displayed for theanesthesiologist by means of the display means.

For example, the following measured values, which are variable overtime, can be displayed for a general surgical procedure on an otherwisehealthy patient, who is intubated and respirated: heart rate, meanarterial blood pressure, end-expiratory CO₂ partial pressure, as well asthe BIS value (Bispectral Index Monitoring, BIS Index for short, anindicator of the “depth of anesthesia” measured on the basis of an EEG).

Depending on the therapeutic procedure and the patient's context (e.g.,co-morbidities), parameters may be eliminated or additional parametersmay be important. For example, the respiration rate, the O₂ saturationand the tidal volume may be additionally displayed in case of atherapeutic procedure during which the patient is breathingspontaneously. The ST segment of the ECG (electrocardiogram) beingrecorded simultaneously as well as the inspiratory oxygen concentrationmay be additionally displayed in another example, in case of a surgicalprocedure during which the oxygen supply of the myocardium is relevantbecause of a past disease of the coronary vessels of the heart.

It is possible according to the present invention, for the first timeever, to make available to the anesthesiologist the informationnecessary for optimally controlling the anesthesia in such an easilyaccessible manner that the anesthesiologist can control and monitor theanesthesia with improved safety and precision. Since theanesthesiologist can recognize, for the first time ever, an interactionbetween information on the anesthetic or anesthetics being used andinformation on the actions of the anesthetics on the patient, whichactions also depend on the procedure and/or the anesthesia, theanesthesiologist can improve the instantaneously necessary dispensing ofthe anesthetics being used as well as the necessary depth of anesthesia.

The present invention makes possible, furthermore, a reduced cognitivework load for the anesthesiologist due to the combination of individual,combined as well as mutually relevant information in one display or adisplay device. This may lead to a less early onset of fatigue of theanesthesiologist, as well as to improved course of anesthesia andincreased patient safety compared to the procedure known from the stateof the art.

The combination of information that pertains to the anesthetics beingused as well as information that pertains to the instantaneousphysiological status of the patient in a combined display device makesit, moreover, possible to obtain clues on whether the active ingredientmodels, which are always based on patient population statistics andaccording to which concentrations are determined, are also true in theindividual case and whether these can be brought into line with theindividual patients actually being treated and whether these can bechecked on the basis of this patient. Corrections may possibly have tobe made in the controlling of the anesthesia on the basis of therecognized deviations of the patient's behavior from the hypotheticalmodel behavior, which in turn makes it possible to improve theanesthesia.

The present invention has, furthermore, the object of providing aprocess by means of which a combined anesthetic effect of a combinationof active ingredients on the patient being anesthetized can bedetermined. Another object of the present invention is to provide adevice suitable herefor and to propose an anesthesia device.

This object is accomplished according to the present invention by aprocess for determining a combined anesthetic effect on a patient beinganesthetized by means of a combination of active ingredients. Theprocess comprises the step of determining the concentration of eachactive anesthetic ingredient at the site of action, combining theactions of all active ingredients, including combining the actions ofall active ingredients within each class of active anestheticingredients used and determining a synergistic interaction between theactive anesthetic ingredients used for the anesthesia.

The concentration of every active ingredient is determined here at thesite of action. Knowledge of the actual action of the active ingredientadministered on the patient is thus of particular interest according tothe present invention, contrary to the knowledge of the concentrationalone, at which the active ingredient is present in the blood. In casesin which it is not possible to determine the actual concentration of oneor more active ingredients at the site of action by measurement, thisconcentration may be replaced with the second most accurateconcentration that can be measured. The concentration of each drug atthe site of action can be determined with pharmacokinetic and/orpharmacodynamic models.

The action of all active ingredients used is combined in the processaccording to the present invention, and each active ingredient can betaken into account individually here, or a cluster formation isperformed at first, by means of which active ingredients of one classare combined. Combination can be defined according to the presentinvention, for example, as an addition of the efficacy or potency of theactive ingredients if they act on the same type of receptor orreceptors. However, if they act according to mutually different actionmechanisms, the actions of the active ingredients being used arecombined corresponding to the type of interaction of these activeingredients, for example, either additively, synergistically orantagonistically. The interaction is additive, for example, betweenopiates, and the corresponding concentrations of the opiates being usedat the sites of action can be added up in a scaled manner based on therespective C50 or EC50 values (corresponding to a mean efficacy orpotency).

The procedure described generally above in connection with theanalgesics is followed in the case of the sedatives/hypnotics (orvolatile anesthetics, intravenous anesthetics) used. Volatile hypnoticscan be “added up,” for example, by means of a scaling to the MAC value(minimal alveolar concentration) concerning their efficacy.

Furthermore, a synergistic interaction between a plurality of, i.e., atleast two active ingredients used for anesthesia is determined in theprocess according to the present invention. This interaction can bedescribed by means of models, as they were published, e.g., by Greco W.R., Bravo G., Parsons J. C. The search for synergy: a critical reviewfrom a response surface perspective. Pharmacol. Rev. 1995 June; 47(2):331-385; Minto C. F., Schnider T. W., Short T. G., Gregg K. M.,Gentilini A., Shafer S. L. Response surface model for anesthetic druginteractions. Anesthesiology, 2000 June; 92(6): 1603-1616; Bouillon T.W., Bruhn J., Radulescu L., Andresen C., Shafer T. J., Cohane C., ShaferS. L. Pharmacodynamic interaction between propofol and remifentanilregarding hypnosis, tolerance of laryngoscopy, bispectral index, andelectroencephalographic approximate entropy. Anesthesiology 100 (6):1353-1372, 2004; and Bouillon T. W., Schumacher P. M., Leibundgut D.,Shafer S. L., Zbinden A. M. A Novel Mechanistic Model Based on the MACReduction Paradigm Describes Hypnotic-Opioid Interaction for Suppressionof Responses to Stimulation. Anesthesiology 2004; 101: A503. The fullrelated contents of the publications cited are part of the presentdisclosure by reference.

In case of interactions that are not (yet) known from the state of theart, it is possible to extrapolate over the mean efficacy or potencybetween the drugs of one type of drug each (i.e., analgesics, on the onehand, or sedatives/hypnotics, on the other hand).

In case of volatile anesthetics, this can be done, in turn, by means ofthe Minimum Alveolar Concentration (MAC—a measure of potency foranesthetics) values, and this can be done by means of the C50 or EC50values in the case of opiates.

The action of all active ingredients can be combined and a combinedpotency N, which is obtained from the drug types scaled over the meanefficacy or potency and an interaction term, can be described by meansof such interaction models as well as the knowledge of the respectiveconcentrations of the active ingredients at the site of action and thecombination of the action of all active ingredients. The combinedpotency N can be shown via an inverted sigmoid function to a onedimensional range of, e.g., 0 to 100, or 0 to 10 or to a range scaledcorrespondingly differently (e.g., by means of simple multiplication bya factor or division by that factor). The combined potency N cantherefore be stated, for example as NSRI (Noxious Stimulus ResponseIndex):

$\begin{matrix}{{N\; S\; R\; I} = {100*{\left( {1 - \frac{\left( {N/N^{\prime}} \right)^{sl}}{1 + \left( {N/N^{\prime}} \right)^{sl}}} \right).}}} & (1)\end{matrix}$

This NSRI index corresponds to the probability of a reaction or responseof the patient to a painful stimulus. By skillfully selecting N′ and s1(see below), a favorable working range can be defined concerning, e.g.,the tolerance of a painful stimulus or the wakability of the patient.NSRI equals 100 in case of an alert and non-anesthetized patient, and ithas the value 0 in case of the deepest anesthesia, and the values 0 and100 are to be considered to be purely exemplary. The possible range ofvalues may also be between other values. The display is therefore notlimited to a scale of 0 to 100. Other displays are possible as well. Inparticular, the value range of NSRI can be changed, e.g., by lineartransformation. The NSRI can be stated as a dimensionless numericalvalue. Moreover, it can indicate a prospective trend over time. Itsdisplay is comparable in this embodiment to the display of parametersfor indicating the depth of anesthesia, such as the BIS obtained bymeans of EEG. In particular, it can be displayed in a time-relatedmanner, i.e., with reference to concrete points in time in the future.

A plurality of graphic comparison values for controlling the anesthesiaand for the wakability of the patient, e.g., an NSRI, at which 50% ofthe patients would tolerate laryngoscopy, can be integrated in thedisplay to support the anesthesiologist. These comparison values arebased, e.g., on known population values.

To estimate the interaction, the NSRI may be plotted additionally forcomparison for one drug, for example, the sedative/hypnotic only. N iscalculated for this (according to the calculation instructions of theselected interaction model) as if no analgesic (e.g., an opiate) hadbeen administered. The NSRI is now calculated, as before, by means offormula (1). An analgesic effect—consisting of the direct effect of theanalgesics and the gain in action based on synergistic interaction withthe sedatives/hypnotics—can be estimated from the difference between thereduced NSRI thus calculated and the combined NSRI (also taking intoaccount the analgesics). However, as can be recognized by the personskilled in the art, calculation alone, e.g., of an analgesic componentor of the component of other drugs used, such as the hypnotic orsedative or of an interaction term is also possible by means of thepresent invention and is also covered by same.

The following model is suitable for displaying the depth of anesthesiaas a continuum of sedation up to the lack of response to noxious ordisturbing stimuli on a time-based scale. The following hypothesis makesit possible to display a response probability of the patient and acumulated action of the active ingredient on an integrated scale.

The standard interaction surface model can be expressed as:

$\begin{matrix}{P = \frac{N^{g}}{1 + N^{g}}} & (2)\end{matrix}$in which

-   -   P is the probability of tolerating a certain stimulus;    -   N is the combination of the active ingredient concentrations,        standardized by means of C50 values corresponding to them and        corrected by the interaction effect; and    -   g is a slope factor, which indicates the slope of the        concentration-vs.-response curve.

The formula

$\begin{matrix}{N = \frac{C_{hyp}}{C\; 50_{hyp}*A_{out}}} & (3)\end{matrix}$in which

$\begin{matrix}{A_{out} = {A_{in}*\left( {1 - \frac{C_{opi}}{{C\; 50_{opi}} + C_{opi}}} \right)}} & (4)\end{matrix}$applies to the sequential response model.

A_(out) indicates a stimulus intensity in case of effects due toadministered opioids, and A_(in) indicates the stimulus intensity in theabsence of opioids (A_(in)=1 indicates the “calibrating stimulusintensity”); consequently, the model describes the damping of thestimulus by the opioid.

C_(hyp) and C_(opi) indicate the concentrations of the hypnotic and ofthe opioid or of the respective combinations thereof, and C50_(xxx) thecorresponding C50 or EC50 values corresponding to the mean efficacy orpotency. N is therefore a dimensionless value, which indicates thecombined “effective concentrations” and is obviously independent fromthe intensity of the stimulus (A_(in)=1). They may not appear to beparticularly intuitive at first glance, but it should be borne in mindthat the relative damping to a stimulus is fully independent from thestimulus intensity, and that the value N necessary for the tolerance ofa stimulus is calculated with inclusion of the stimulus intensity (seebelow).

Plotting N over time yields the corresponding time curve. The ratio ofthe concentrations to the action(s) of these concentrations is displayedas follows: the action(s) or selected endpoints can be displayed asranges of tolerance probabilities (50%-90%) over time on an “action”scale. This requires the calculation of the necessary action for givenprobabilities.

The general surface equation (Equation (2)) can be solved for N. Thisyields

$\begin{matrix}{N = \left( \frac{P}{1 - P} \right)^{1/g}} & (5)\end{matrix}$

Formula

$\begin{matrix}{{A_{out} = A_{in}},{N = \frac{C_{hyp}}{C\; 50_{hyp}*A_{in}}}} & \left( {{6\; a},{6\; b}} \right)\end{matrix}$is obtained by substituting Equation (3) and simplification based on theabsence of opioids.

An N′ can be calculated only as a function of the stimulus intensityA_(in), the desired tolerance probability P and the known slope factorg:

$\begin{matrix}{N^{\prime} = {\left( \frac{P}{1 - P} \right)^{1/g}*A_{in}}} & (7)\end{matrix}$

Examples of a tolerance of shaking and loud shouting (TOSS) with anA_(in=)1 by definition and tolerance of laryngoscopy (TOL) A_(in)=2.83(corresponding to the C50 ratio of propofol for the tolerance oflaryngoscopy as well as tolerance of shaking and loud shouting accordingto Bouillon T. W., Schumacher P. M., Leibundgut D., Shafer S. L.,Zbinden A. M., A. Novel: Mechanistic Model Based on the MAC ReductionParadigm Describes Hypnotic-Opioid Interaction for Suppression ofResponses to Stimulation. Anesthesiology, 2004; 101: A50.

The use of a slope factor g of 3.46—as is estimated by means ofsequential interaction modeling of propofol and remifentanil (cf.literature reference above)—yields the values in N units in Table 1below.

Probabilities [N units] P50% TOSS 1 P90% TOSS 1.89 P50% TOL 2.83 P90%TOL 5.34

Rescaling of N—especially when high anesthetic concentrations arereached—and the necessary resealing of the axis designations associatedherewith as well as the resealing of the calibration lines of the TOLand TOSS ranges can be advantageously avoided by means of aretransformation using a sigmoid function of the following form:

$\begin{matrix}{{N\; S\; R\; I} = {100*\left( {1 - \frac{\left( {N/N^{\prime}} \right)^{sl}}{1 + \left( {N/N^{\prime}} \right)^{sl}}} \right)}} & (8)\end{matrix}$

-   -   in which    -   N′ is the specific N′ value at which an NSRI of 50% is reached;        and    -   s1 is a slope factor for the transformation of N into NSRI.

In case of a definition as in Equation (8), the NSRI has the value of100 (i.e., without the use of active ingredients), if it is calculatedas an example over NSRI=100*(1−(N/2.83)^(s1)/(1+(N/2.83)^(s)1) in theconscious patient, and NSRI trends towards the value 0 during thedeepest anesthesia (i.e., at high concentrations of active ingredients).

This above-described one dimensional scaling to values between 0 and 100has the added advantage that the anesthesiologist is usually experiencedin the handling of indicators, whose values are between 0 and 100, with0 representing the deepest anesthesia and 100 the conscious patient(e.g., BIS, entropy).

If, as in the above example, N′=2.83, a 50% NSRI would correspond totolerance of laryngoscopy by 50% of the patients (see Table 1), whichcorresponds to a reasonable choice. The slope factor should be set suchthat a good working range is obtained for the anesthesia range as wellas for the wake-up range. If s1=2.18, the 90% tolerance of laryngoscopyis shown on an NSRI of (exactly) 20, and the wake-up range (90% to 50%TOSS) is shown as an NSRI of about 70 to 90.

The following configuration is proposed for a conventionalpharmacokinetic/pharmacodynamic display, which is used in clinicalroutine for carrying out the present invention:

-   -   1. Display of the NSRI over time with predictions for the future        based on current drug dosages;    -   2. Display of the NSRI with hypnotic drugs (hypothesis that no        opioids were administered and there is no interaction) in the        display, combined as in the above item (same axes);    -   3. Display of the concentration of hypnotic active ingredients        (blood/end tidal and site of action) on separate axes over time        with predictions for the future;    -   4. Displays of the concentration of one or more opioids (blood        and site of active ingredient) on different axes over time with        predictions for the future;    -   5. Provision of the possibility of inserting markers, bars        and/or lines for individualizing the display of the active        ingredient; and    -   6. Display of a wake-up prediction (especially display of the        foreseeable point in time of wake-up).

Furthermore, the possible combinations may be very helpful:

-   -   1. Display of the hemodynamic status over time (pulse rate,        blood pressure);    -   2. Display of processed EEG parameters over time (e.g., BIS,        entropy); and    -   3. Display of other parameters of the multidimensional patient        status, which are relevant for the anesthesia, over time.

The processes according to the present invention may be implemented withthe respective devices according to the invention as well as with ananesthesia device, which may be designed, e.g., as a respirator (alsoknown as a ventilator). Since the above-described advantages can also begained to the full extent with the devices according to the presentinvention, reference is expressly made here to the above discussion ofthese devices to avoid repetitions. Advantageous variants are alsodiscussed herein as well.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be explained in more detail below on thebasis of the attached drawings, identical reference numbers designatingidentical structures and/or components. In the drawings:

FIG. 1 is a schematic simplified view of a device according to thepresent invention with a display means;

FIG. 2 is a view of the contents of a display device of an exemplaryembodiment according to the present invention;

FIG. 3 is a view showing a form of display according to the presentinvention; and

FIG. 4 is a view showing values of the NSRI according to the presentinvention for certain intraoperative events.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in particular, FIG. 1 shows a schematicsimplified view of a device 1 according to the present invention formonitoring a patient. This device 1 is designed, for example, as ananesthesia device, but the present invention is not limited to a devicefor monitoring an anesthesia. The device 1 has two i.v. pumps 3 and 5for two anesthetics, wherein at least one of the pumps 3 and 5 for i.v.administration may also be designed as a means for administering avolatile anesthetic. Device 1 has, furthermore, an interface 7, by meansof which data can be entered via a keyboard, a mouse or the like, notshown. Device 1 has, furthermore, an information management system 9, bymeans of which connection can be established between the anesthesiadevice, a hospital information system, a network and the like forproviding data that are relevant in the particular case. Data from thei.v. pumps 3, 5 as well as from the interface 7 also enter thisinformation management system 9. Information or data 11 on thedispensing of a first anesthetic by means of the i.v. pump 3 are sent inthe device 1 according to the present invention shown in FIG. 1 to afirst pharmacokinetic model 13. Information or data 15 on the dispensingof a second anesthetic administered by the i.v. pump 5 are sent to asecond pharmacokinetic model 17. A pharmacodynamic model 19 receivesinformation or data on the name, type or ID of the first anestheticused, which is administered by the i.v. pump 3, as well as comparabledata 23 on the second anesthetic administered by the i.v. pump 5. Thetwo pharmacokinetic models 13 and 17 as well as the pharmacodynamicmodel 19 receive, furthermore, demographic data 25 on the patient beinganesthetized. These demographic data 25 can be entered via the interface7 or stored and are available for polling in the information managementsystem 9. Furthermore, clinical observations 27 and other events can bepassed on via the interface 7 and/or the information management system 9for display in a display 29. For this, the display 29 has a means 31 formarking or indicating the onset of the event. A storage means 33 as wellas a reproduction means 35 are attached to the display 29. Calculated orpredicted data 37, 39 concerning the effect-time concentrations of thedrugs administered can be sent by means of the first pharmacokineticmodel 13 and the second pharmacokinetic model 17 (which may becomplemented by additional models) to the display 29 for display in aconcentration-based display 41 and/or in a time-based display 43. Data45 sent from the pharmacokinetic model 19, which receives data frommodels 13 and 17—see the respective data stream indicated by broken linein FIG. 1—to the display 29, as they will be explained below inreference to FIG. 2.

FIG. 2 shows a possible display according to the present invention onthe display device 29 of a monitoring device according to the presentinvention. The pulse rate (HR, heart rate), the mean arterial pressure(MAP), as well as the expiratory CO₂ content ( CO₂) are plotted overtime (see section VI) in an upper section of the view in FIG. 2, whichis designated by I.

The BIS is displayed as an indicator of the depth of anesthesia overtime in section II. The index NSRI proposed according to the presentinvention is displayed as an another indicator of the depth ofanesthesia on a scale from 0 to 100 in section III. The concentration ofsevofluran over time is displayed in section IV, the concentration ofremifentanil in section V, easily recognizable for the anesthesiologistat any time, the data in Ce[vol. %] corresponding to the concentrationat the respective site of action.

The view in FIG. 2 shows in section VI other events marked by thereference numbers 51, 53 and 55, which may designate various events,such as skin incision, intubation, etc., during the anesthesia. Thedisplay of these events in the context with other pieces of information,such as time curve, dispensing of the drugs, etc., may provide theanesthesiologist with additional important information and relationshipsor explain such information or explain such information orrelationships.

As can be seen on the right-hand side of the view in FIG. 2 undermarking VII, displays directed towards the future can also be taken intoaccount in the display according to the present invention. Thus, aconcentration of sevofluran as well as remifentanil is shown in anisobole view in a concentration-based diagram VIII. Values that are inthe past are marked in bold here and carry the reference number 57. Theinstantaneous concentration ratio of the two anesthetics (sevofluran andremifentanil) is marked by the dot with reference number 59. Aprediction of what anesthetic concentrations and stimulus toleranceswill be present in the near future (5 minutes or 10 minutes) isdisplayed by the curve 61 marked less bold as well as the trendindicated by means of arrow 63 in a clearly recognizable manner for theanesthesiologist. Concerning display VIII, reference is made, moreover,to the patent application with the German Patent Application number DE10 2006 053 856.0-32 (which is hereby incorporated by reference in itsentirety). The full content of this application related to this subjectis thus part of the present disclosure by reference.

FIG. 3 shows two views of displays, which belong together and which havebeen generated during the anesthesia of the patient rendered anonymousunder the designation “T01G0300.” The upper view in FIG. 3 correspondsto a view that is the subject of the above-mentioned German PatentApplication of this applicant bearing the number 10 2006 053 856.0-32.Reference is therefore made here for explanation to the application. Thelower view in FIG. 3 shows the curve 65 of NSRI over the duration of theanesthesia.

Furthermore, the lower view shows two ranges 67 and 69 shown as shadedareas. Range 67 ranges here from an NSRI of 20 to an NSRI of 50. Range69 ranges from an NSRI of 70 to an NSRI of 90. The range designated by67 represents a range in which 90% to 50% of the patients toleratelaryngoscopy in this embodiment. Range 69 represents a range in which50% of the patients do not respond to shaking and loud shouting.

FIG. 4 shows a view according to the present invention of the NSRI forcertain intraoperative events, namely, intubation 71, skin incision 73and extubation 75 from the anesthesia of 35 patients, to whom propofolwas administered together with remifentanil and fentanyl.

A first range 77 shown as a shaded area (which corresponds to range 69in FIG. 3) is limited by the 90% TOSS as well as the 50% TOSS (Toleranceto Shaking and Shouting) and is prominently displayed (e.g., in color)on the display or display device for easier orientation for theanesthesiologist. This also applies to a second range 79, which islikewise shown as a shaded area (which corresponds to range 67 in FIG.3), which is limited by the 90% and 50% TOL (tolerance of laryngoscopy).

The distributions of the NSRI for three events 71, 73 and 75 over the 35patients are indicated by the reference numbers 81, 83 and 85.

Display 87 shows the NSRI curve 65 of a patient rendered anonymous with“T24G0300” over time.

Thus, the present invention provides a process for monitoring a patientbeing anesthetized as well as a process for determining a combinedeffect of different anesthetics used. It proposes, furthermore, devicesfor carrying out the process according to the present invention.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

1. An anesthetic process comprising the steps of: providing ananesthetic administrating device capable of administrating a pluralityof anesthetics to a patient; operating said anesthetic administratingdevice thereby administrating a plurality of active anestheticingredients to the patient; providing an information management systemreceiving data from said anesthetic administrating device; providing aplurality of models connected to said information management system,said models: determining a concentration of each of the activeanesthetic ingredients at a site of action; determining a potency ofeach of the active anesthetic ingredients from the determinedconcentrations of each active anesthetic ingredient at the site ofaction; determining an interaction relationship between each of theactive anesthetic ingredients; combining the potencies according theinteraction relationship to obtain a combined potency of all theplurality of active anesthetic ingredients; converting said combinedpotency to a Noxious Stimulus Response Index (NSRI), said NSRI being aone-dimensional parameter having a full scale range with a firstendpoint of said range indicating an alert and non-anesthetized patient,and with a second endpoint of said range indicating a deepestanesthesia, said NSRI being calculated by${NSRI} = {100*\left( {1 - \frac{\left( {N/N^{\prime}} \right)^{sl}}{1 + \left( {N/N^{\prime}} \right)^{sl}}} \right)}$where: N is the combined potency; N′ is a specific value at which anNSRI of 50% is reached; and sl is a slope factor for the transformationof N into NSRI; providing a display connected to said models; displayingthe NSRI on said display.
 2. An anesthetic process in accordance withclaim 1, wherein: the interaction relationship is calculated using amathematical formula based on the individual potencies of each of theactive anesthetic ingrediens.
 3. An anesthetic process in accordancewith claim 1, further comprising: grouping the active anestheticingredients into different classes based on action mechanisms; combiningthe potencies for each of the active anesthetic ingredients in eachclass to determine a class potency; determining an interactionrelationship between the different classes of active anestheticingredients; combining the class potencies according to the interactionrelationship to obtain the combined potency of all the plurality ofactive anesthetic ingredients.
 4. An anesthetic process in accordancewith claim 3, wherein: said step of determining an interactionrelationship is performed using a mathematical formula.
 5. An anestheticprocess in accordance with claim 1, wherein: said combined potency ofthe active anesthetic ingredients are based on a mean anestheticefficacy of the active ingredients used and an interaction term.
 6. Ananesthetic system comprising: an anesthetic administrating devicecapable of administering a plurality of anesthetics to a patient;information management system receiving data from said anestheticadministrating device; a plurality of models connected to saidinformation management system, said models: determining a concentrationof each of the active anesthetic ingredients at a site of action;determining a potency of each of the active anesthetic ingredients fromthe determined concentrations of each active anesthetic ingredient atthe site of action; determining an interaction relationship between eachof the active anesthetic ingredients; combining the potencies accordingthe interaction relationship to obtain a combined potency of all theplurality of active anesthetic ingredients; converting said combinedpotency to a Noxious Stimulus Response Index (NSRI), said NSRI being aone-dimensional parameter and having a full scale range with a firstendpoint of said range indicating an alert and non-anesthetized patient,and with a second endpoint of said range indicating a deepestanesthesia, said NSRI being calculated by${NSRI} = {100*\left( {1 - \frac{\left( {N/N^{\prime}} \right)^{sl}}{1 + \left( {N/N^{\prime}} \right)^{sl}}} \right)}$where: N is the combined potency; N′ is a specific value at which anNSRI of 50% is reached; and sl is a slope factor for the transformationof N into NSRI; a display connected to said models for displaying theNSRI on said display.